The invention relates to drilling fluids and, more particularly, to a thermally stable drilling fluid including an additive which provides thermal stability and enhanced fluid loss control.
Drilling fluids are commonly used in the process of drilling bore holes in subterranean formations. Oil-based drilling fluids are known and used for recovering oil as well as gas. However, a general problem that remains in the industry is that commercially available drilling fluids demonstrate unsatisfactory thermal stability and, after exposure to temperatures higher than about 300.degree. F., tend to exhibit a decrease in rheological properties such as gel strength and yield point, as well as a decrease in fluid loss control.
Furthermore, known drilling fluids typically include many ingredients, most of them of solid nature, which make the drilling fluid expensive. Since large volumes of fluid are used in the course of drilling, the various ingredients have a large economic impact on the overall drilling procedure. This kind of additive in conventional drilling fluids is further undesirable since solids can cause damage to the formation during drilling.
It is therefore clear that the need remains for a thermally stable fluid system which can be used at temperatures higher than 350.degree. F. which will maintain rheological properties and fluid loss control at such high temperatures, and which is economically desirable while minimizing formation damage.
It is therefore the primary object of the present invention to provide a thermally stable drilling fluid having an additive for enhancing thermal stability and maintaining fluid loss control at high temperature.
It is a further object of the present invention to provide a thermally stable drilling fluid system wherein fewer ingredients than conventionally necessary are used to provide a suitable fluid.
It is a still further object of the present invention to provide a thermally stable drilling fluid system wherein solid content and subsequent potentiality for formation damage are reduced.
Further objects and advantages of the present invention will appear hereinbelow.